EXTRA examples

To access this screen:

Run the EXTRA process from the command line by typing 'extra'. Specify an input file, output file and (optionally) retrieval criteria and click OK - the Expression Translator displays.

For more information on the EXTRA process, see EXTRA.

EXTRA Background

The ways in which EXTRA can be used are endless. This section provides a few ideas of what it can do.

Before EXTRA starts to process records from the input file, it must define which fields will appear in the output file. It is important to understand that all decisions about fields in the output file are made before any records are processed.

Normally, the fields that appear in the output are:

All fields that are in the input file
Fields created in the transforms you specify.

You can reduce the number of fields in the output file by using saveonly(), keep() and erase() functions. There are examples of these functions below.

Examples

Add a record-number field

The process COPYNR copies a file, adding a RECORDNO field as it does. The same can be achieved using EXTRA. This example shows how the first() and prev() function can be used:

if (first())

RECORDNO = 1

else

RECORDNO = prev(RECORDNO)+1

end

Add comments

EXTRA statements can be supported by comments, for example:

!START M1

!EXTRA &IN(MOD2), &OUT(t)

# Comment 1

NEWFLD = 1

# Comment 2

NEWFLD2=9999

# Comment 3

!END

Comments are not supported within IF loops. The following statement, for example, will cause EXTRA to fail:

VAL2 = PVALUE*1.5

if (VAL2 == 8)

# comment is here

VAL5 = 5

END

Alphanumeric field functions

The following example illustrates the functions for alphanumeric fields. It creates a new alphanumeric field, s1, with a length of 40 characters and assigns to it the comma-separated list of field values. The trim() function is used to remove trailing spaces from the BHID field. The string() function is used to convert numeric fields to character strings (with two decimal places), and the join() function is used to concatenate the various bits into a single alphanumeric value. Note that all unwanted fields can be erased with a single use of the erase() procedure:

s1;a40 = join(trim(BHID), ", ",

  string(FROM, 2), ", ",

  string(TO, 2), ", ",

  string(Cu, 2), ", ",

  string(Zn, 2))

erase(BHID, FROM, TO, Cu, Zn)

The resulting file could be OUTPUT, and then loaded into Microsoft Excel or another package as a comma-separated values (CSV) file. (This function is available directly in OUTPUT, but this method gives finer control on the number of decimals, etc.)

Apply capping in a new field

AU_C=AU

if(AU_C>35) AU_C=35 end

..and here's another way:

AU_C = min(AU, 35)

atan2 (2-dimensional arctangent)

The function atan2() is a two-argument arctangent function. It calculates the angle ( \theta ) between the positive x-axis and the point ((x, y)) in the Cartesian plane. This angle is measured in radians and ranges from (-\pi) to (\pi) 12.

The atan2() function is particularly useful because it takes into account the signs of both (x) and (y) to determine the correct quadrant of the angle. This makes it more reliable than the single-argument arctangent function, which only returns values between (-\pi/2) and (\pi/2) 2.

The result is an angle in degrees within the range -180.0 and +180.0.

Examples:

atan2(1, 1)

Returns ( \pi/4 ) (45 degrees), which is the angle in the first quadrant.

atan2(-1, -1)

Returns (-3\pi/4 ) (-135 degrees), which is the angle in the third quadrant.

Note: the order of the arguments is (x, y) (as in Microsoft Excel) and not (y, x) as used in other programming languages.

azimuth()

EXTRA provides azimuth(dx, dy) to return the azimuth in degrees of a line from (0, 0) to (dx, dy). The result is a value between 0.0 and 360.0. If dx and dy are both zero, the absent data indicator is returned. For example, to find the azimuth of each segment in a string:

AZI = azimuth(next(XP)-XP, next(YP)-YP)

Create a new field

You define a new field by typing its name, a specification for its type and the value to be assigned. If the field is numeric and explicit, you do not need to specify the type.

For example:

C = (A + B)/2 # C is an explicit, numeric field

You add the specification for other types of fields after the field name, like this:

BHID;a12 = "RC1000" # explicit alphanumeric field, 12 characters

XMORIG;ni = 10200 # implicit numeric field

VERSION;a24i = "Resource estimate 2Q24" # implicit alphanumeric field, 24 characters

The letter "a" means "create an alpha field" and "i" means "create an implicit field". For an alphanumeric field, you should specify the maximum size of the field, in characters. It you omit it, the field size will be 4 characters.

You can also create a field with the same specification as an existing field:

BHID2;[BHID] = BHID # BHID2 has the same specification as BHID

This means "Create a field called BHID2, make it the same type as the existing BHID field and then set it to the same value as the BHID field".

Create an Implicit Field

EXTRA can also create implicit fields. Consider this example:

XMORIG;ni = 10200.0

YMORIG;i = 20100.0

ZMORIG;i = 273.0

REVISION;a20i = "Resource study 2Q24"

This will create four new implicit fields: three numeric fields and one alphanumeric field. The "i" character can be placed anywhere in the specification except inside the length specification. For example, the following all achieve the same result:

REVISION;a20i = "Resource study 2Q24"

REVISION;ia20 = "Resource study 2Q24"

REVISION;ai20 = "Resource study 2Q24"

REVISION;i20a = "Resource study 2Q24"

REVISION;20ai = "Resource study 2Q24"

REVISION;20ia = "Resource study 2Q24"

Degrees, minutes and seconds

EXTRA can convert degrees, minutes and seconds to decimal degrees and vice-versa. Starting with fields dd, mm, and ss, EXTRA can easily create a field containing decimal degrees:

# Change dd, mm, ss to decimal degrees

dms = dd + mm/60 + ss/3600

The field dms now contains decimal degrees. To change them back, use the following:

dd = int(dms)

mm = mod(int(60*dms), 60)

ss = int(10*mod(3600*dms, 60) + 0.5)/10

The final expression rounds-off the seconds field, ss, to the nearest 1/10th.

Don't forget that if you are writing the expressions in a script or a macro then the keyword go must be entered on the last line.

Delete all but the last record in a drillhole

if(BHID==next(BHID)) delete() end

erase()

The erase() procedure specifies a list of fields that you do not want in the output file. Like keep(), you can specify multiple erase instances, and you can erase in combination with both saveonly() and keep() calls.

For example, this call to saveonly() requests that 9 fields are written to the output file.

saveonly(BHID, FROM, TO, LENGTH, X, Y, Z, A0, B0)

Add 3 fields to this list using keep(), which is like saveonly(), but adds to an existing list:

keep(CU, PB, ZN)

Now use erase() to remove items from the list. In this case, the three coordinate fields:

erase(X, Y, Z)

Here, saveonly() specifies 9 fields that will be written and keep() specifies three more. Then, erase() removes three fields from the list (X, Y and Z).

exit()

The procedure exit() immediately terminates processing before the current record has been written. This may be useful if a condition is found that means processing further records in unnecessary. For example:

if (BHID != prev(BHID)

exit()

end

keep()

keep() is used to define the fields that will be in the output file. It is like saveonly(), but the field lists are cumulative. If you specify:

keep(BHID, FROM, TO, LENGTH, X, Y, Z, A0, B0)

… followed by

keep(CU, PB, ZN)

… then all 12 fields are written to the output. You can use as many keep lists as you like. All the fields in all the lists are saved.

The "keep" procedure may be useful if you need to save different fields in different circumstances, for example:

saveonly("BHID", "FROM", "TO", "LENGTH", "X", "Y", "Z", "A0", "B0")

if (type("AU") != "") keep("AU") end

if (type("CU") != "") keep("CU") end

Here, all the standard static drill hole fields are saved, plus "AU" and/or "CU" if they exist.

IJK Block Model Field Functions

EXTRA has a set of functions for creating and querying a block model index field, IJK.

To use these functions, you must be processing a block model file. Otherwise, EXTRA will fail.

ijkget()

ijkget() returns values encoded into the block model index. Here are some examples:

Return the x-direction parent cell index:

II = ijkget(IJK, "I")

Return the y-direction parent cell index

JJ = ijkget(IJK, "J")

Return the z-direction parent cell index

KK = ijkget(IJK, "K")

Return the x-coordinate of the parent cell

XX = ijkget(IJK, "X")

Return the y-coordinate of the parent cell

YY = ijkget(IJK, "Y")

Return the z-coordinate of the parent cell

ZZ = ijkget(IJK, "Z")

The second argument may be upper or lower case.

If you are processing a rotated block model, all X, Y, and Z coordinates are in the model coordinate system.

ijknum()

ijknum() combines separate I, J and K indexes into a single IJK index. For example:

IJK = ijknum(II, JJ, KK)

xyzijk()

xyzijk() creates an IJK index number from X, Y and Z model coordinates. For example:

IJK = xyzijk(XX, YY, ZZ)

Here's a worked example to shift a cell eastwards by one parent block size:

II = ijkget(IJK, "I") NOT CHECKED!!

JJ = ijkget(IJK, "J")

KK = ijkget(IJK, "K")

II = II + 1

IJK = ijknum(II, JJ, KK)

XC = XC + XINC

Missing Fields Management

If EXTRA tries to use a field that does not exist, it will report an error and stop processing the file. This can be an inconvenience if you want to erase a field and are not sure if it exists.

There are now two ways to deal with this.

@FLDFAIL

You can specify @FLDFAIL=0 in the command line. This means "don't fail if a field does not exist". Alternatively, @FLDFAIL=1 (the default setting) means that EXTRA will fail if it tries to use a missing field.

When you specify @FLDFAIL=0 and EXTRA encounters a missing field, it creates the field and set its value to the absent data indicator (for example, "-").

Note: @FLDFAIL=0 does not just apply to the arguments to erase; if @FLDFAIL=0, EXTRA never fails because of a missing field. This means that if your transform contains "A=B+C" and either of the fields B or C do not exist in the file, they are created and assigned a "missing" value. In this example, the value assigned to field A will also be an absent data indicator.

type()

The second way to avoid “missing field” errors is to use the type() function.

type() returns a string of characters that describe the type of the field. If a field does not exist, type() returns an empty string (""). So, to detect if a field exists, you could specify something like this:

if (type("B") == "") B = 0 end

Note: the argument passed to type is a text string and therefore you must enclose it in double-quotes. If you just pass the field name (i.e. "type(B)" ), EXTRA may report that the field does not exist and stop.

not(expr)

The function not(expr) inverts the truth of the expression. In EXTRA, a numeric expression is "false" if its value is zero and "true" if its value is not zero. You usually use relational expressions in conditional (if) statements. Often, inverting the sense of the expression makes it easier to read:

if (not(last())) delete() end

This deletes every record in the file except the last one, which could be useful if EXTRA is used to accumulate values.

Numeric value handling

EXTRA handles numeric values in the following way and in the order shown:

Scientific notation: “1.23e” is interpreted as a NUMBER (1.23e+0 or 1.23)
Value signing: “-” is interpreted as “minus”
"5" is interpreted as the number 5.

Hence, “1.23e-5” becomes 1.23 - 5 = -3.77.

Random numbers

Extra can generate pseudo random numbers.

You can return a uniformly distributed pseudo-random number between 0.0 and 1.0 using rand():

rand()

EXTRA also permits generation of a random value between two bounds. For example, to generate a random value between 10 and 20;

randbetween(10,20)

There is an, optional process parameter @SEED which you may use to control the starting value for the pseudo-random sequence. This may be useful when debugging a procedure, for example. If @SEED=0, or is negative or is not specified, EXTRA uses a starting number based on the current date and time.

Note: the RANDOM process can also be used to generate random values.

rownum()

Sometimes it is useful to add a row number field to a file. You can now do this simply by using the rownum() function:

RECORD = rownum()

You could also use this in conditional statements:

if (rownum() > 1000) exit() end

Or, to retain only every 10th record:

if (mod(rownum(), 10) != 0) delete() end

This means "if the remainder you get when you divide the row number by 10 is not zero, delete the record".

saveonly()

saveonly() specifies a list containing all the fields you want in the output. For example:

saveonly(BHID, FROM, TO, LENGTH, X, Y, Z, A0, B0)

If you specify saveonly() more than once, the list of fields in the last saveonly is the one used. So if you specify:

saveonly(BHID, FROM, TO, LENGTH, X, Y, Z, A0, B0)

followed by:

saveonly(CU, PB, ZN)

EXTRA will only save the fields CU, PB and ZN.

Note: keep() is like saveonly() but fields are added cumulatively.

Sort fields

The SORTX or MGSORT process can be used to sort records into increasing or decreasing order.

That said, consider the example of five fields, a, b, c, d and e, and you want to shuffle their values such that the value assigned to a is less than or equal to the value assigned to b, and b is <= c, c <= d and d <= e.

The following EXTRA transformations do this, and also show that it is not necessary to place every transformation on a separate line:

if (a > b) t = a a = b b = t end

if (b > c) t = b b = c c = t end

if (c > d) t = c c = d d = t end

if (d > e) t = d d = e e = t end

if (a > b) t = a a = b b = t end

if (b > c) t = b b = c c = t end

if (c > d) t = c c = d d = t end

if (a > b) t = a a = b b = t end

if (b > c) t = b b = c c = t end

if (a > b) t = a a = b b = t end

erase(t)

special()

The special function is used to decode any reserved values of your application. For example, MININT and MAXINT. These are the smallest and largest 32-bit integers. They may be useful in conjunction with randbetween(), for example:

R0 = randbetween(0, special(MAXINT))

This returns a positive random value of the entire integer range supported by your application.

type(name)

EXTRA provides a type(name) function which returns the type of the named field.

For example, for a field called "X", then type("X") returns:

• "n" if X is a numeric, explicit field.

• "ni" if X is numeric and implicit.

• "a8" if X is an alphanumeric field of length eight.

• "a8i" if X is an alphanumeric, implicit field with length eight.

• "" if the field X does not exist.

Important: the argument to type must be a string and not the name of a field. This is so that type does not fail if the field does not exist (and @FLDFAIL=1). For example, "A;a4=type("BHID")" is probably correct whilst "A;a4=type(BHID) evaluates the field BHID to obtain the name of a field, and is probably incorrect.

Unusual field names

If a field name contains characters that are part of the EXTRA syntax, you should enclose the name in square brackets, like this:

[AU-FINAL] = (AUOK + AU_IPD)/2

You must enclose AU-FINAL in square brackets because it contains a minus-sign, which would be interpreted incorrectly.

Note: the legacy method for allowing unusual field names was to enclose the name in single quotes. This is still supported but we recommend using square brackets in new scripts or macros. You should also use this form if EXTRA would interpret the field name as a number.